0000000000172345
AUTHOR
David Vie
Large scale synthesis of nanostructured zirconia-based compounds from freeze-dried precursors
Nanocrystalline zirconia powders have been obtained at the multigram scale by thermal decomposition of precursors resulting from the freeze-drying of aqueous acetic solutions. This technique has equally made possible to synthesize a variety of nanostructured yttria or scandia doped zirconia compositions. SEM images, as well as the analysis of the XRD patterns, show the nanoparticulated character of those solids obtained at low temperature, with typical particle size in the 10–15 nm range when prepared at 673 K. The presence of the monoclinic, the tetragonal or both phases depends on the temperature of the thermal treatment, the doping concentration and the nature of the dopant. In addition,…
A new approach to the synthesis of intermetallic compounds: mild synthesis of submicrometric CoxMy (M = Mo, W; x∶y = 3∶1 and 7∶6) particles by direct reduction of freeze-dried precursors
A simple processing route to cobalt–molybdenum and cobalt–tungsten intermetallics (CoxMy, where M = Mo and W, and x∶y = 3∶1 and 7∶6) has been developed, on the basis of the use of precursors resulting from freeze-drying of aqueous solutions of the appropriate common metal salts. The influence of the preparative variables on the outcomes of this procedure is examined. These compounds are prepared as single phases by thermal reduction of amorphous freeze-dried powders under a hydrogen–argon atmosphere (8% H2), followed by slow cooling of the samples. The materials have been characterised by X-ray powder diffraction, metal analysis, scanning electron microscopy and thermogravimetry under an ox…
Nano-sized mesoporous carbon particles with bimodal pore system and semi-crystalline porous walls
Acetylene CVD carbon replication of a hierarchical pore silica-based material, Fe-UVM-7, is reported. The original template organization, which is based on the aggregation of mesoporous nanoparticles, is accurately replicated in the final carbon material: a bimodal porous carbon combining mesoporous nanoparticles and inter-particle textural-like pores which provide high surface area, a highly accessible pore system and semi-crystalline pore walls in the form of graphitic-like nanodomains is presented.
Nanostructured Solids from Freeze-Dried Precursors: Multigram Scale Synthesis of TiO2 -Based Powders
Nanocrystalline TiO2 and Ti1−xVxO2 (x = 0.01) powders have been prepared by thermal decomposition, in air, of amorphous precursors resulting from the freeze-drying of appropriate solutions. In addition, TiO2−xNy (anatase and rutile) and TiOxNy (rock-salt) have been prepared by thermal treatment in ammonia of a crystalline precursor (TiO2 obtained at 673 K). TEM and SEM images, as well as the analysis of the X-ray diffraction (XRD) patterns, show the nanoparticulated character of those solids obtained at low temperatures, with typical particle sizes in the 10–20 nm range when prepared at 673 K. The UV–Vis results indicate both the insertion of V in the anatase lattice and the feasibility of …
Generalized “one-pot” preparative strategy to obtain highly functionalized silica-based mesoporous spherical particles
In this work we present a synthesis strategy for the preparation of Stöber-type mesoporous particles functionalized with inorganic species. The procedure is based on a combination of the Atrane and the Stöber methods. Both as a source of silicon and of the incorporated heteroelements (Fe, Zn, Al, Ti) the corresponding atrane complexes are used as hydrolytic reagents. These complexes are easily formed by reaction with triethanolamine. Mesoporosity is achieved using surfactant micelles as templates. Obtaining uniform spherical particles is achieved by optimizing the amount of water-ethanol in the reaction medium. The particle sizes have been modulated by controlling simple parameters such as …